Hi, I have implemented Direct in Dial Trunks (DIDs) in Canada using a
Mitel SX100 PBX in 1986
but I would not advise you to use this technology. It really doesn't
offer any advantage over digital lines
The first problem is that the three or four digits that get passed to
the PBX must represent extension number directly or must be mapped to an
extension range (a feature not always available).
The second limitation is the number of simultanious calls
All in all, the technology is better left to history.
A digital trunk servicing each extension is far less expensive and
offers much more flexability.
I would see if you can port the existing number range to an ITSP (or get
a consecutive group of digital lines)
These trunks could then directly ring an extension and if unanswered
could be diverted to a receptionist
to take messages or go to Vmail. This is the basic functionality of
analog DID and is a "piece of cake" to implement with Asterisk.
Henry
[EMAIL PROTECTED] wrote:
That's what I don't understand John. This analog signalling is common in
the US as well. The old TASCOM PBX that we have was built in Chino, CA.
Analog DID lines seem to be commonly supported on the old as well as new
PBXs (for compatibility reasons). I think this was done because the PBX has
considered an autonomous unit: self powered and self provisioned, hands
off by the Telco. The only reason I can think that Asterisk doesn't support
the full version of DID directly is that no one has worked on drivers for the
cards. Brooktrout seems to have some. This looks like a gaping hole to me.
The E&M Winkstart applies only to E1 digital connections. Sure DID is
supported on Asterisk, but only in terms of the dialing protocol. Anyone else
have any insight into this lack of support for the full DID trunk line circuits?
Are we talking legacy here? Is ISDN expected to fill the gap? If so, this cuts
out support for small message service businesses (in some locales) that
can't afford a T1/E1. Of course, the digital deals are probably better in other
markets. Maybe T1s are less that $1K in the larger cities.
Thanks,
Peter M.
On Wed, 2006-07-26 at 16:23 -0300, [EMAIL PROTECTED] wrote:
Perhaps some of you are not aware of how the old DID lines work. When the incoming call
is transferred to one of these trunks, 48 volts must be present. The CO switch seizes the
line and polarity is reversed by the PBX to indicate ability to receive the call. This is called
wink start. Four digits from the bank of DID numbers are then transferred and the call is
connected. It is a standard ability of a real PBX since it has been traditionally assumed that
DID trunking can be handled by a PBX. In fact, a lot of the new IP PBXs out there do this
form of DID, also known as DID-over-analog. A few of these lines are much cheaper to run
than a T1. That's why I'm disappointed that there doesn't seem to be any direct support for
DID cards on Asterisk. We have two sets of these trunk lines to support but it needs to
function for the messaging service to start.
According to
http://www.voip-info.org/wiki/index.php?page=Asterisk+config+zapata.conf
Asterisk supports the following signalling types:
* em: E & M Immediate Start
* em_w: E & M Wink Start
...
The description you gave above seems to be E & M Wink start.
I hadn't been aware of this type of signaling until you brought this up.
Is it commonly available in Canada?
John
********************************************************
Peter MacFarlane, ACP
Network Administration & Programming
Target Call Center/ Message Centre P.E.I.
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Henry L.Coleman [ VoIP-PBX ] Tel.1 866 415-5355 Ext.301
